Nowadays, with the maturity of automatic feeding technologies, automatic document feeders (ADF) are widely used in scanners, printers or any other office machines. By the automatic document feeders, many documents are automatically and successively fed into these office machines in order to achieve the labor-saving purpose. In a case where the automatic document feeder is an idle state (e.g. before the documents are fed into the office machine), the documents are stopped at a position in front of an entrance of a transfer channel by a document stopper of the automatic document feeder. Consequently, the documents are stopped from being introduced into the transfer channel.
Please refer to FIGS. 1˜4. FIG. 1 is a schematic side view illustrating the structure of a conventional automatic document feeder, wherein the automatic document feeder is in an idle state. FIG. 2 is a schematic partial perspective view illustrating some components of the conventional automatic document feeder of FIG. 1 and taken along another viewpoint. FIG. 3 is a schematic side view illustrating the structure of the conventional automatic document feeder of FIG. 1, wherein the automatic document feeder is in a working state. FIG. 4 is a schematic partial perspective view illustrating some components of the conventional automatic document feeder of FIG. 3 and taken along another viewpoint.
The automatic document feeder 1 comprises an upper cover (not shown), an input tray 11, a transfer channel 12, a pick-up arm 13, a driving shaft 14, a restriction element 15, and a document stopper 16. The pick-up arm 13 is located near an entrance of the transfer channel 12. The driving shaft 14 is penetrated through the pick-up arm 13, and pivotally coupled to the upper cover. When the driving shaft 14 is driven by a motive power source (not shown) to be rotated, the pick-up arm 13 is correspondingly moved from a first position X1 (see FIG. 1) to a second position X2 (see FIG. 3) or moved from the second position X2 to the first position X1. Moreover, the pick-up arm 13 comprises a pick-up roller 131 and a separation roller 132. When the automatic document feeder 1 is in the working state, the pick-up arm 13 is moved to the second position X2. Consequently, the uppermost document P11 on the input tray 11 is picked up by the pick-up roller 131 to be fed into the transfer channel 12. The separation roller 132 is used for separating the uppermost document P11 and the underlying document P12 on the input tray 11 from each other, thereby preventing multiple documents P1 from being simultaneously fed into the transfer channel 12.
Moreover, the document stopper 16 comprises a rotating shaft 161, a sustaining part 162, and a stopping part 163. The rotating shaft 161 is penetrated through the region between the sustaining part 162 and the stopping part 163, and pivotally coupled to the upper cover. The restriction element 15 is fixed on a sidewall of the pick-up arm 13. When the automatic document feeder 1 is in the idle state, the pick-up arm 13 is moved to the first position X1. Under this circumstance, the stopping part 163 of the document stopper 16 is arranged between the documents P1 and the entrance of the transfer channel 12. In addition, since the sustaining part 162 of the document stopper 16 is contacted with the restriction element 15, the swinging action of the document stopper 16 relative to the rotating shaft 161 will be limited by the restriction element 15. At this moment, the range of allowing the document P11 on the input tray 11 to swing the document stopper 16 in the direction D1 is limited to a very small extent. Consequently, the documents P1 are stopped from being introduced into the transfer channel 12.
When the automatic document feeder 1 is in the working state, the pick-up arm 13 should be moved to the second position X2. As the pick-up arm 13 is moved, the restriction element 15 is correspondingly moved in a direction away from the sustaining part 162 of the document stopper 16. Under this circumstance, the sustaining part 162 of the document stopper 16 is no longer limited by the restriction element 15, and thus the sustaining part 162 of the document stopper 16 can be freely swung relative to the rotating shaft 161. Meanwhile, the document P11 which is disposed on the input tray 11 and moved forwardly by the pick-up roller 131 can easily push the stopping part 163 of the document stopper 16. Consequently, the document stopper 16 is swung in the direction D1 and conveniently introduced into the transfer channel 12. After the document P11 is completely introduced into the transfer channel 12, since the stopping part 163 of the document stopper 16 is no longer pushed by the document P11, the document stopper 16 is swung to its original position in the direction D2 in response to the gravity force.
However, in some situations, the automatic document feeder 1 still has some drawbacks. For example, in a first situation, after the document feeding task is ended, the pick-up arm 13 of the automatic document feeder 1 is ascended from the second position X2 to the first position X1. In a second situation, during the document P11 is fed into the transfer channel 12, the pick-up arm 13 should be temporarily ascended from the second position X2 to the first position X1 in order to achieve the maximum functions of the automatic document feeder 1 with the minimum motive power source. Under these situations, if the document P11 is not stayed at the original position where the automatic document feeder 1 is in the idle state, the pick-up arm 13 of the conventional automatic document feeder 1 may fail to be moved from the second position X2 to the first position X1 because the pick-up arm 13 is influenced by the document stopper 16. If the pick-up arm 13 is reluctantly driven to be moved from the second position X2 to the first position X1, the possibility of causing damage of the document P11 is increased.
Please refer to FIGS. 5 and 6. FIG. 5 is a schematic side view illustrating the conventional automatic document feeder of FIG. 1 during the pick-up arm is ascended from the second position to the first position, in which the document is not stayed at the original position where the automatic document feeder is in the idle state. FIG. 6 is a schematic partial perspective view illustrating some components of the conventional automatic document feeder of FIG. 5 and taken along another viewpoint.
As shown in FIGS. 5 and 6, during the pick-up arm 13 of the conventional automatic document feeder 1 is ascended from the second position X2 to the first position X1, the document P11 is stayed at a position higher than its original position X4 where the automatic document feeder 1 is in the idle state. Meanwhile, since the stopping part 163 of the document stopper 16 is contacted with the front end of the document P11, the document stopper 16 fails to be swung to its original position in response to the gravity force. Under this circumstance, when the pick-up arm 13 is ascended in the direction toward the first position X1 to a third position X3, which is arranged between the first position X1 and the second position X2, the sustaining part 162 of the document stopper 16 is contacted with the restriction element 15. Consequently, the pick-up arm 13 fails to be continuously ascended. If the pick-up arm 13 is reluctantly driven to be ascended, the restriction element 15 is conveniently forced to push the sustaining part 162 of the document stopper 16, so that the document stopper 16 is swung in the direction D2. Under this circumstance, since the front end of the document P11 is pushed by the stopping part 163 of the document stopper 16, the document P11 is possibly damaged.
Moreover, during the pick-up arm 13 of the conventional automatic document feeder 1 is moved from the first position X1 to the second position X2, if the stopping part 163 of the document stopper 16 is excessively pushed by the document P11, the movement of the pick-up arm 13 is hindered. FIG. 7 is a schematic side view illustrating the conventional automatic document feeder of FIG. 1, in which the stopping part of the document stopper is excessively pushed by the document and the movement of the pick-up arm is hindered. As shown in FIG. 7, since the stopping part 163 of the document stopper 16 is excessively pushed by the front end of the document P11, the sustaining part 162 of the document stopper 16 is contacted with the restriction element 15. Consequently, a force F1 is applied to the region between the sustaining part 162 and the restriction element 15. Meanwhile, the magnitude of the torque for the force F1 to rotate the driving shaft 14 is equal to F1×R1, wherein R1 is a vertical distance of the force F1 from an axel center of the driving shaft 14. In other words, for driving the movement of the pick-up arm 13 from the first position X1 to the second position X2, the rotation of the driving shaft 14 should surmount the torque F1×R1.
Therefore, there is a need of providing an improved automatic document feeder in order to eliminate the above drawbacks.